1. Field of Invention
The present invention relates to an optical remote control system and a light source control method therefor, in particular to such optical remote control system and light source control method which are capable of modulating a light source for better orientation.
2. Description of Related Art
Many current interactive video game systems provide users with joysticks or remote controllers so that the users can play the games by actions, e.g. to drive a race car, to swing a golf club, etc. Such joystick or remote controller typically includes a gyro, an accelerometer, or an image sensor. In a joystick or remote controller which employs the image sensor, the image sensor senses images and generates information for controlling the movement of a cursor or a pointer on a screen, or for selecting an icon to execute a corresponding function or program, etc.
FIG. 1A shows a schematic diagram illustrating the use of a joystick in a prior art interactive video game system. The orientation of the joystick 11 is identified according to the images captured by the image sensor 111. That is, the positions of the light beams from the multiple lighting units 131 of the light source 13 in the images captured by the image sensor 111 are used to confirm the orientation of the joystick 11 such that, e.g., a cursor 141 on the display 14 is accurately moved from the left side to the right side. Referring to this figure, the light source 13 comprises six lighting units 131 which are all turned on to light during operation of the game system, to form one light spot in the image captured by the image sensor 111. However, if the distance between the joystick 11 (or the image sensor 111) and the light source 13 is too short, the light beams from the multiple lighting units 131 form a bigger light spot in the image captured by the image sensor 111, and the short distance may cause overexposure such that it is hard to recognize the light spot in the captured image. On the contrary, if the distance between the joystick 11 and the light source 13 is too far, the light spot formed by the light beams from the lighting units 131 in the image captured by the image sensor 111 is likely to be too small and hard to be recognized. Therefore, the distance between the conventional joystick 11 and the light source 13 needs to be kept within a proper workable range, otherwise the light spot in the captured image is oversize or undersize.
FIGS. 1B-1C show schematic diagrams illustrating the light spot in the image captured by the image sensor. Referring to FIG. 1B, when the distance between the image sensor and the light source is L, the width of the visible region resulting from the visible angle 152 of the image sensor is W, and the light spot 151 in the image 15 covers four pixels. Referring to FIG. 1C, when the distance between the image sensor and the light source is 2 L, the width of the visible region resulting from the visible angle 152′ of the image sensor is 2 W, and the light spot 151′ in the image 15′ covers two pixels. If the recognizable range of the light spot is 2-4 pixels, then the light spot is not recognizable if it covers less than two pixels or more than four pixels. This means that the operating distance of the prior art is L−2 L. If the operating distance is smaller than L or larger than 2 L, the system cannot properly respond.
The limited operating distance or operating range is disadvantageous; the light spot is smaller than the required minimum size and cannot be recognized when the distance is longer than the maximum operating distance, and the light spot image is larger than the required maximum size and cannot be recognized when the distance is shorter than the minimum operating distance. If the size of the light spot is enlarged to increase the maximum operating distance, the minimum operating distance is adversely affected. On the contrary, if the size of the light spot is decreased to shorten the minimum operating distance, the maximum operating distance of the light spot image is also shortened.
In view of above, the present invention overcomes the foregoing drawbacks by providing an improved optical remote control system and a light source control method. The operating distance of the optical remote control system can be enlarged by adjusting the number and the positions of the lightened units of the light source for the orientation. The light spot becomes recognizable more accurately in a wider range, and the lighting units can be controlled in an optimal way to effectively save the power of the light source.